Receptor tyrosine kinases (RTKs) have been shown to be important as therapeutic targets against lung cancer. However, even with the RTK epidermal growth factor receptor inhibition, the response with small molecule inhibitors is at best 5%-15% in refractory advanced NSCLC. We have recently identified that c-Met is overexpressed in NSCLC and NSCLC and may potentially serve as an important therapeutic target in lung cancer. C-Met is a RTK important in cell proliferation, motility, invasion, metastasis, angiogenesis, wound healing, and tissue regeneration. The ligand for c-Met is the hepatocyte growth factor (HGF). Utilizing immunohistochemical analysis, we show that 69% of adenocarcinoma tissue samples, 71% of squamous cell carcinoma samples, and 78% of large cell carcinomas have c-Met overexpression as compared to adjacent normal tissues. In some of the NSCLC tumor tissue samples, we also show activation of c-Met (in the juxtamembrane domain at pY1003 and autophosphorylation sites at pY1230/1234/1235). As preliminary data, we have analyzed the c-Met gene in 127 lung adenocarcinoma tumor tissue samples and have identified unique mutations in the regulatory juxtamembrane domain and the semaphorin domain (at the Nterminus of c-Met). Interestingly, we did not find any mutations in the tyrosine kinase domain of c- Met. We have also been able to obtain small molecule inhibitors and inhibitory antibodies against c- Met and show specific growth inhibition in NSCLC cell lines and in vivo mouse xenograft models. Our hypothesis is that c-Met is an important therapeutic target in NSCLC. We will determine the specific role of c-Met and therapeutic targeting of c-Met in NSCLC via these specific aims: 1. Determine the role of c-Met/HGF axis and mutations of c-Met in biological and biochemical functions of non-small cell lung cancer cells;2. Determine the in vitro and in vivo effects of inhibiting c-Met in NSCLC;3. Determine the effects of c-Met/HGF signaling and inhibition on PI3K/AKT/mTOR pathway in NSCLC;4. Conduct an anti-c-Met phase I/I I clinical trial against NSCLC. Through the achievement of the goals proposed in these specific aims, we will arrive at novel therapy against c- Met in lung cancer.